Most hearing devices include an earmold which is inserted and retained in the pinna and/or the ear canal of the user. Some hearing devices like headphones or earphones use standard sized earmold to fit a number of listeners. Unfortunately, such standard earmolds offer poor fit and poor comfort to the hearing device user. While for other hearing devices like in hearing aids, a customized earmold is generally produced. FIG. 1A illustrates a diagram of a human ear that is, for example, the ear of a user of the hearing device. Specifically, the ear 100 has various identifiable parts, or features, such as, for example, aperture 102, crus 103, canal 104, concha 105 and cymba 106. As one skilled in the art will recognize, in order to produce a customized earmold for a patient, an ear impression is typically taken. Various processes for taking such ear impressions have been developed, but most such processes typically involve an audiologist using a quick foam that is cured to make a mold of the patient's ear, including that of the ear canal. For this purpose, the foam is introduced into the ear of the patient (user), and the foam may be cured by using conventional curing methods. The cured mold is then removed and the cured mold provides an impression including contours of the different parts of the ear, such as parts 102-106 of FIG. 1A. Such an ear impression reflecting the parts of ear 100 of FIG. 1A is shown in FIG. 1B. More particularly, ear impression 101 has aperture portion 102A corresponding to aperture 102 of FIG. 1A; crus portion 103A corresponding to crus 103 of FIG. 1A; canal portion 104A corresponding to canal 104 in FIG. 1A; concha portion 105A corresponding to concha 105 of FIG. 1A; cymba portion 106A corresponding to cymba 106; and lower body portion 107A.
The cured mold is then sent to a manufacturing site for producing a hearing aid with the customized mold for that particular patient. Even though this customized mold is useful relative to the standard earmold, multiple iterations may be required in order to achieve the earmold that provides a satisfactory fit for the patient.
In hearing aids, the design of the earmold also considers acoustic parameters such as feedback and occlusion issues for providing an acceptable fit. However, the satisfactory fit of the custom-fit earmold for the hearing device is generally described in terms of comfortable fit and retention capability of the custom-fit earmold in the ear and/or ear canal of the user. Retention of the earmold in the ear canal is typically accomplished by friction. Friction is created by radial pressure of the earmold on the wall of the ear canal. The more pressure, the greater is the retention force.
However, friction is dependent on lubricants between the earmold and the wall of the canal. The presence of cerumen (ear wax), perspiration or water significantly reduces friction retention. Retention of the earmold based on friction is also susceptible to loosening caused by forces, like forces exerted on the earmold by jaw movement, which tends to dislodge the earmold from its desired position.
Furthermore, existing literature proposes incorporating Electroencephalography (EEG) electrodes in hearing aids. However, it is essential to ensure good skin contact with electrodes in order to obtain reliable noise free EEG signals during daily use of the hearing aid.
Therefore, there is a need of a solution allowing for modeling, including a mathematical image representation and/or manufacturing, a custom-fit earmold that offers a comfortable, stable and reliable fit in the ear canal of the user and may also provide a possible positioning of the EEG electrodes on the custom fit ear mold.